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Cranial anatomy of the Late Triassic phytosaur Machaeroprosopus, with the description of a new species from West Texas

Published online by Cambridge University Press:  07 October 2013

Axel Hungerbühler ,
Bill Mueller ,
Sankar Chatterjee  and
Douglas P. Cunningham
Axel Hungerbühler
Affiliation:
Mesalands Community College, 911 S. Tenth Street, Tucumcari, NM 88401, USA. Email: [email protected]
Bill Mueller
Affiliation:
Division of Paleontology, Museum of Texas Tech University, Box 43191, Lubbock, TX 79409, USA
Sankar Chatterjee
Affiliation:
Division of Paleontology, Museum of Texas Tech University, Box 43191, Lubbock, TX 79409, USA
Douglas P. Cunningham
Affiliation:
Division of Paleontology, Museum of Texas Tech University, Box 43191, Lubbock, TX 79409, USA
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Abstract

The skull anatomy of a new species of the phytosaur Machaeroprosopus is described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred to Machaeroprosopus sp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process. Machaeroprosopus lottorum n. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with bevelled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal, Machaeroprosopus lottorum n. sp. bridges the morphological gap between species previously referred to the genera Pseudopalatus and Redondasaurus. A parsimony analysis of known species of Machaeroprosopus supports the hypothesis that the development of the rostral crest in Machaeroprosopus is a sexually dimorphic feature, and questions the validity of the genus Redondasaurus. Consequently, Redondasaurus is here considered a junior synonym of Machaeroprosopus.

Keywords

DockumNorianPseudopalatusRedondasaurus
Type
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Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 103 , Issue 3-4: The Full Profession: A Celebration of the Life and Career of Wann Langston, Jr., Quintessential Vertebrate Palaeontologist , September 2012 , pp. 269 - 312
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Copyright © The Royal Society of Edinburgh 2013 

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